What is pollution flashover?

　Pollution flashover in electrical equipment refers to the phenomenon where, under humid conditions, the contaminants attached to the insulating surface of electrical equipment have their soluble substances gradually dissolve in water, forming a conductive layer on that insulating surface. This reduces the insulation level of the insulator, leading to intense discharge phenomena under the influence of electric fields. 　There are many measures to prevent flashover. Traditional methods include performing cleaning operations during the spring and autumn seasons, as well as using coatings such as silicone oil and silicone grease, and properly adjusting the creepage distance of the external insulation. In recent years, anti-flashover creepage skirts and RTV anti-flashover coatings have been employed. 　　1. Short-acting silicone oil: The usage method is to, once a year in spring and autumn, after shutting down and cleaning outdoor high-voltage electrical equipment, wipe off the previous silicone oil and apply a new layer. Due to its certain degree of insulation and water repellency, silicone oil plays a role in preventing flashover ； However, due to its short shelf life of about half a year, and the fact that it remains in a non-cured state, it tends to attract dust, which can lead to flashover in rainy or foggy weather, and even more serious consequences. 　　2. Reasonable creepage adjustment 　Creepage adjustment refers to increasing the creepage distance of the external insulation of electrical equipment in order to improve the insulation level. For example, increasing the number of insulator units in dirty areas, or using dust-proof insulators, glass insulators, and composite insulators. Operating experience shows that in areas with severe pollution, the use of new insulator strings provides better anti-pollution effects, but such products are only suitable for transmission lines. Additionally, methods for increasing the creep resistance of insulator strings involve adjusting the minimum air gap between the live conductors and the tower, adjusting the distance between the live conductors and the lower crossarm, and verifying wind deflection after adjusting for creep resistance. 　　3. Anti-pollution flashover creep assistance skirt: The material commonly used for anti-pollution flashover creep assistance skirts is synthetic silicone rubber. This type of skirt is attached to existing porcelain insulators or ceramic insulators; by adding curves and increasing the distance at which flashover can occur, the flashover voltage is elevated. Furthermore, due to the good insulation and water-repellent properties of synthetic silicone rubber, dust on its surface is not easily soaked by water, which prevents the formation of flashover paths and thus reduces the likelihood of pollution-induced flashover. However, the synthetic silicone rubber anti-pollution flashover climbing aid skirts also present some technical issues in use; for example, the insulator columns must be extremely clean and smooth during bonding, and the adhesive must be applied evenly – otherwise, uneven joints are prone to dust accumulation, or the adhesive may crack and dry out ； For example, due to differences in manufacturing processes and raw material quality among manufacturers, some products are highly prone to damage, breaking, deformation, cracking, and so on. 　　4. Single-component RTV power anti-fouling coating In recent years, single-component RTV (Room Temperature Vulcanized Silicone Rubber) power anti-fouling coatings have been widely used in the field of preventing fouling in power systems as a new technology and material, thanks to their outstanding advantages such as long durability and no need for maintenance, achieving significant results. 　　One-component RTV coatings possess excellent water-repellent properties and resistance to water migration, which significantly increase the pollution flashover voltage of the external insulation in power transmission and distribution equipment; this pollution flashover voltage can be increased by more than twice compared to porcelain insulators without such coatings. Hydrophobicity refers to the situation where the forces between the molecules of a non-polar solid medium and the water molecules on its surface are weaker than the cohesive forces between water molecules themselves; as a result, the water on its surface forms isolated droplets rather than a continuous water film. The hydrophobic migration of RTV refers to the phenomenon where the hydrophilic dust contaminants present on the surface of the RTV coating become hydrophobic after a certain period of time; in other words, the hydrophobicity of the RTV coating migrates to the surface of the contaminant layer ； At this point, when water droplets are sprayed on its surface, the dirty layer becomes difficult to be saturated due to its hydrophobic nature; only discrete water beads remain on the surface of the dirty layer. This property **improves the resistance of electrical equipment to pollution-induced flashover. 　　One-component RTV power anti-pollution flashover coatings possess excellent electrical, physical, and chemical properties. Its breakdown voltage is above 17 KV/mm ； Can operate for extended periods in the range of –40°C to +80°C, with stable temperature resistance ； Good adhesion to porcelain insulators ； It can achieve surface drying after 30 minutes of spraying at room temperature, cure within 24 hours, and remain elastic over the long term ； Resistant to acids, alkalis, and oil corrosion; does not bubble, wrinkle, change color, or peel off as a result ； Resistant to environmental aging; the coating does not crack, flake, peel, or detach under natural conditions, with an outdoor service life of over 5 years. It can be used on the external insulation of electrical equipment in industries and areas with high dirt and pollution levels, such as power plants, chemical plants, steel mills, and cement factories, offering significant effects in preventing flashover.

Surface discharge caused by contamination on the dielectric surface is abbreviated as pollution flashover. Measures to prevent pollution flashover: ① Regularly clean and wash insulators and insulating sleeves with water. ② Improve the structure of insulators so that they can clean themselves in windy or rainy conditions. ③ Increase the clearance distance. ④ Apply hydrophobic materials such as semiconductor glazes or silicone oil to the insulator surfaces. ⑤ Try to keep high-voltage transmission lines away from polluted areas, and avoid building high-voltage substations in such areas

I’ve learned how to deal with \"dirty flash\"!